sparse array not returned

[rveltz]

I have been willing to try this fantastic tool but I am not able to get the result. Basically, the call to forwarddiff_color_jacobian seems slow and it does not return a sparse jacobian.

It is possible that I am not using your package very well... I am posting this in case of a bug:

using SparsityDetection, SparseArrays, SparseDiffTools, ForwardDiff, Test

source_term(x; a = 0.5, b = 0.01) = 1 + (x + a*x^2)/(1 + b*x^2)
function F_chan(x, α, β = 0.)
	f = similar(x)
	n = length(x)
	f[1] = x[1] - β
	f[n] = x[n] - β
	for i=2:n-1
		f[i] = (x[i-1] - 2 * x[i] + x[i+1]) * (n-1)^2 + α * source_term(x[i], b = β)
	end
	return f
end

N = 100
_input = rand(N)
_output = similar(_input)

The jacobian is

_J = ForwardDiff.jacobian(x -> F_chan(x, 3.,0.01), _input) |> sparse
colors = matrix_colors(_J)
@show maximum(colors) # this returns 3

Then, the issue:

# does not return sparse array
J = @time forwarddiff_color_jacobian(x -> F_chan(x, 3.,0.01), _output; colorvec = colors, sparsity = _J, jac_prototype = _J)

Thank you for your help,

[ChrisRackauckas]

It should be giving back a sparse matrix? https://github.com/JuliaDiff/SparseDiffTools.jl/blob/master/src/differentiation/compute_jacobian_ad.jl#L91

[rveltz]

I am not sure what you are implying, that I passed wrong options?

[ChrisRackauckas]

No, we are doing something wrong, and I honestly cannot figure out why. Reading the logic sounds like it should give back a sparse. @huanglangwen can you take a look?

[huanglangwen]

That's due to sparse + dense -> dense at J = J + Ji.

[ChrisRackauckas]

Oh yes tricky. Awesome!

@JuliaRegistrator register()

[JuliaRegistrator]

Registration pull request created: JuliaRegistries/General/8441

After the above pull request is merged, it is recommended that a tag is created on this repository for the registered package version.

This will be done automatically if Julia TagBot is installed, or can be done manually through the github interface, or via:

git tag -a v1.3.2 -m "<description of version>" 280cbf4fc5b3bbd6b0f9b1da28b81b573102600a
git push origin v1.3.2

[rveltz]

Thank you!